In general, when a light-sensitive material is subjected to mechanical stresses such as twisting, bending, and suction during the production process, or during transportation after production, or during the handling for development or the like, the silver halide emulsion layer is also subject to such stresses. This exerts adverse influences on its photographic performances, causing undesirable problems such as desensitization, sensitization, and fog.
In recent years, the development of light-sensitive material has been speeded up and automated. Therefore, the light-sensitive material is liable to be bent or sucked during its transportation, and the degree of such bending or suction has become increasingly severe. This results in the application of high mechanical stresses on the silver halide emulsion layer. It has, therefore, been desired to develop a light-sensitive material which is improved in its resistance against such mechanical stresses.
In order to improve the stress resistance of light-sensitive materials, attempts have been made to improve the physical properties, e.g., flexibility, of a gelatin-containing hydrophilic layer (hereinafter referred to as a "gelatin layer").
For example, U.S. Pat. No. 2,960,404 discloses the addition of polyhydric alcohols such as glycerin, ethylene glycol, and 1,6-hexanediol to the gelatin layer, and British Pat. No. 738,637 discloses the addition of dialkyl phthalate. The addition of such compounds, however, suffers from serious disadvantages in that when the gelatin layer containing such compounds is placed under high temperature and high humidity conditions, the adhesion strength of the gelatin layer to a support is weakened, or contrarily the surface of the gelatin layer becomes excessively sticky, causing the problem of sticking to another surface.
Japanese patent application (OPI) Nos. 37919/72 (corresponding to U.S. Pat. No. 3,773,517), 21133/74 (corresponding to U.S. Pat. No. 3,967,966), 46018/78 (corresponding to U.S. Pat. No. 4,197,127), 109831/79 (corresponding to U.S. Pat. No. 4,301,240), and 76137/79 (corresponding to U.S. Pat. No. 4,145,221) (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), and Japanese Patent Publication Nos. 20432/74 (corresponding to British Pat. No. 1,293,252) and 24887/72 (corresponding to U.S. Pat. No. 3,620,751), etc., disclose techniques of increasing the dimensional stability and stress resistance of a silver halide emulsion layer by using polymer latexes having flexibility in combination with gelatin as binders for the silver halide emulsion layer.
Polymer latexes as used in such techniques are latexes containing an ester (e.g., a lower alkyl ester) of an ethylenically unsaturated carboxylic acid, such as acrylic acid and methacrylic acid, as a major recurring unit. The addition of such polymer latexes, however, is liable to cause problems such as desensitization, increased fog, loss of transparency during development and an increase in surface electric resistance.